[libc-commits] [libc] first trailing zero (PR #81526)

via libc-commits libc-commits at lists.llvm.org
Mon Feb 12 12:28:17 PST 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libc

Author: Nick Desaulniers (nickdesaulniers)

<details>
<summary>Changes</summary>

- [libc][stdbit] implement stdc_first_leading_one (C23)
- add tg macros to doc
- [libc][stdbit] implement stdc_first_trailing_zero (C23)


---

Patch is 44.95 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/81526.diff


39 Files Affected:

- (modified) libc/config/linux/x86_64/entrypoints.txt (+10) 
- (modified) libc/docs/stdbit.rst (+30-30) 
- (modified) libc/include/llvm-libc-macros/stdbit-macros.h (+44) 
- (modified) libc/spec/stdc.td (+14-2) 
- (modified) libc/src/__support/CPP/bit.h (+59) 
- (modified) libc/src/stdbit/CMakeLists.txt (+2) 
- (added) libc/src/stdbit/stdc_first_leading_one_uc.cpp (+20) 
- (added) libc/src/stdbit/stdc_first_leading_one_uc.h (+18) 
- (added) libc/src/stdbit/stdc_first_leading_one_ui.cpp (+20) 
- (added) libc/src/stdbit/stdc_first_leading_one_ui.h (+18) 
- (added) libc/src/stdbit/stdc_first_leading_one_ul.cpp (+20) 
- (added) libc/src/stdbit/stdc_first_leading_one_ul.h (+18) 
- (added) libc/src/stdbit/stdc_first_leading_one_ull.cpp (+21) 
- (added) libc/src/stdbit/stdc_first_leading_one_ull.h (+18) 
- (added) libc/src/stdbit/stdc_first_leading_one_us.cpp (+21) 
- (added) libc/src/stdbit/stdc_first_leading_one_us.h (+18) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_uc.cpp (+21) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_uc.h (+18) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_ui.cpp (+20) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_ui.h (+18) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_ul.cpp (+21) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_ul.h (+18) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_ull.cpp (+21) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_ull.h (+18) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_us.cpp (+21) 
- (added) libc/src/stdbit/stdc_first_trailing_zero_us.h (+18) 
- (modified) libc/test/include/stdbit_test.cpp (+30) 
- (modified) libc/test/src/__support/CPP/bit_test.cpp (+13) 
- (modified) libc/test/src/stdbit/CMakeLists.txt (+2) 
- (added) libc/test/src/stdbit/stdc_first_leading_one_uc_test.cpp (+21) 
- (added) libc/test/src/stdbit/stdc_first_leading_one_ui_test.cpp (+21) 
- (added) libc/test/src/stdbit/stdc_first_leading_one_ul_test.cpp (+21) 
- (added) libc/test/src/stdbit/stdc_first_leading_one_ull_test.cpp (+21) 
- (added) libc/test/src/stdbit/stdc_first_leading_one_us_test.cpp (+21) 
- (added) libc/test/src/stdbit/stdc_first_trailing_zero_uc_test.cpp (+20) 
- (added) libc/test/src/stdbit/stdc_first_trailing_zero_ui_test.cpp (+20) 
- (added) libc/test/src/stdbit/stdc_first_trailing_zero_ul_test.cpp (+20) 
- (added) libc/test/src/stdbit/stdc_first_trailing_zero_ull_test.cpp (+20) 
- (added) libc/test/src/stdbit/stdc_first_trailing_zero_us_test.cpp (+20) 


``````````diff
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 75e39ae51fdb06..d53b225e4d87e2 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -117,6 +117,16 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.stdbit.stdc_first_leading_zero_ui
     libc.src.stdbit.stdc_first_leading_zero_ul
     libc.src.stdbit.stdc_first_leading_zero_ull
+    libc.src.stdbit.stdc_first_leading_one_uc
+    libc.src.stdbit.stdc_first_leading_one_us
+    libc.src.stdbit.stdc_first_leading_one_ui
+    libc.src.stdbit.stdc_first_leading_one_ul
+    libc.src.stdbit.stdc_first_leading_one_ull
+    libc.src.stdbit.stdc_first_trailing_zero_uc
+    libc.src.stdbit.stdc_first_trailing_zero_us
+    libc.src.stdbit.stdc_first_trailing_zero_ui
+    libc.src.stdbit.stdc_first_trailing_zero_ul
+    libc.src.stdbit.stdc_first_trailing_zero_ull
 
     # stdlib.h entrypoints
     libc.src.stdlib.abs
diff --git a/libc/docs/stdbit.rst b/libc/docs/stdbit.rst
index 4f242d21f8b842..790a747baaa2da 100644
--- a/libc/docs/stdbit.rst
+++ b/libc/docs/stdbit.rst
@@ -41,31 +41,31 @@ stdc_leading_ones_us         |check|
 stdc_leading_ones_ui         |check|
 stdc_leading_ones_ul         |check|
 stdc_leading_ones_ull        |check|
-stdc_trailing_zeros_uc
-stdc_trailing_zeros_us
-stdc_trailing_zeros_ui
-stdc_trailing_zeros_ul
-stdc_trailing_zeros_ull
-stdc_trailing_ones_uc
-stdc_trailing_ones_us
-stdc_trailing_ones_ui
-stdc_trailing_ones_ul
-stdc_trailing_ones_ull
-stdc_first_leading_zero_uc
-stdc_first_leading_zero_us
-stdc_first_leading_zero_ui
-stdc_first_leading_zero_ul
-stdc_first_leading_zero_ull
-stdc_first_leading_one_uc
-stdc_first_leading_one_us
-stdc_first_leading_one_ui
-stdc_first_leading_one_ul
-stdc_first_leading_one_ull
-stdc_first_trailing_zero_uc
-stdc_first_trailing_zero_us
-stdc_first_trailing_zero_ui
-stdc_first_trailing_zero_ul
-stdc_first_trailing_zero_ull
+stdc_trailing_zeros_uc       |check|
+stdc_trailing_zeros_us       |check|
+stdc_trailing_zeros_ui       |check|
+stdc_trailing_zeros_ul       |check|
+stdc_trailing_zeros_ull      |check|
+stdc_trailing_ones_uc        |check|
+stdc_trailing_ones_us        |check|
+stdc_trailing_ones_ui        |check|
+stdc_trailing_ones_ul        |check|
+stdc_trailing_ones_ull       |check|
+stdc_first_leading_zero_uc   |check|
+stdc_first_leading_zero_us   |check|
+stdc_first_leading_zero_ui   |check|
+stdc_first_leading_zero_ul   |check|
+stdc_first_leading_zero_ull  |check|
+stdc_first_leading_one_uc    |check|
+stdc_first_leading_one_us    |check|
+stdc_first_leading_one_ui    |check|
+stdc_first_leading_one_ul    |check|
+stdc_first_leading_one_ull   |check|
+stdc_first_trailing_zero_uc  |check|
+stdc_first_trailing_zero_us  |check|
+stdc_first_trailing_zero_ui  |check|
+stdc_first_trailing_zero_ul  |check|
+stdc_first_trailing_zero_ull |check|
 stdc_first_trailing_one_uc
 stdc_first_trailing_one_us
 stdc_first_trailing_one_ui
@@ -116,11 +116,11 @@ __STDC_ENDIAN_BIG__
 __STDC_ENDIAN_NATIVE__
 stdc_leading_zeros         |check|
 stdc_leading_ones          |check|
-stdc_trailing_zeros
-stdc_trailing_ones
-stdc_first_leading_zero
-stdc_first_leading_one
-stdc_first_trailing_zero
+stdc_trailing_zeros        |check|
+stdc_trailing_ones         |check|
+stdc_first_leading_zero    |check|
+stdc_first_leading_one     |check|
+stdc_first_trailing_zero   |check|
 stdc_first_trailing_one
 stdc_count_zeros
 stdc_count_ones
diff --git a/libc/include/llvm-libc-macros/stdbit-macros.h b/libc/include/llvm-libc-macros/stdbit-macros.h
index 693a45e63419ff..19b800f342e8ff 100644
--- a/libc/include/llvm-libc-macros/stdbit-macros.h
+++ b/libc/include/llvm-libc-macros/stdbit-macros.h
@@ -86,6 +86,36 @@ inline unsigned stdc_first_leading_zero(unsigned long x) {
 inline unsigned stdc_first_leading_zero(unsigned long long x) {
   return stdc_first_leading_zero_ull(x);
 }
+inline unsigned stdc_first_leading_one(unsigned char x) {
+  return stdc_first_leading_one_uc(x);
+}
+inline unsigned stdc_first_leading_one(unsigned short x) {
+  return stdc_first_leading_one_us(x);
+}
+inline unsigned stdc_first_leading_one(unsigned x) {
+  return stdc_first_leading_one_ui(x);
+}
+inline unsigned stdc_first_leading_one(unsigned long x) {
+  return stdc_first_leading_one_ul(x);
+}
+inline unsigned stdc_first_leading_one(unsigned long long x) {
+  return stdc_first_leading_one_ull(x);
+}
+inline unsigned stdc_first_trailing_zero(unsigned char x) {
+  return stdc_first_trailing_zero_uc(x);
+}
+inline unsigned stdc_first_trailing_zero(unsigned short x) {
+  return stdc_first_trailing_zero_us(x);
+}
+inline unsigned stdc_first_trailing_zero(unsigned x) {
+  return stdc_first_trailing_zero_ui(x);
+}
+inline unsigned stdc_first_trailing_zero(unsigned long x) {
+  return stdc_first_trailing_zero_ul(x);
+}
+inline unsigned stdc_first_trailing_zero(unsigned long long x) {
+  return stdc_first_trailing_zero_ull(x);
+}
 #else
 #define stdc_leading_zeros(x)                                                  \
   _Generic((x),                                                                \
@@ -122,6 +152,20 @@ inline unsigned stdc_first_leading_zero(unsigned long long x) {
       unsigned: stdc_first_leading_zero_ui,                                    \
       unsigned long: stdc_first_leading_zero_ul,                               \
       unsigned long long: stdc_first_leading_zero_ull)(x)
+#define stdc_first_leading_one(x)                                              \
+  _Generic((x),                                                                \
+      unsigned char: stdc_first_leading_one_uc,                                \
+      unsigned short: stdc_first_leading_one_us,                               \
+      unsigned: stdc_first_leading_one_ui,                                     \
+      unsigned long: stdc_first_leading_one_ul,                                \
+      unsigned long long: stdc_first_leading_one_ull)(x)
+#define stdc_first_trailing_zero(x)                                             \
+  _Generic((x),                                                                \
+      unsigned char: stdc_first_trailing_zero_uc,                               \
+      unsigned short: stdc_first_trailing_zero_us,                              \
+      unsigned: stdc_first_trailing_zero_ui,                                    \
+      unsigned long: stdc_first_trailing_zero_ul,                               \
+      unsigned long long: stdc_first_trailing_zero_ull)(x)
 #endif // __cplusplus
 
 #endif // __LLVM_LIBC_MACROS_STDBIT_MACROS_H
diff --git a/libc/spec/stdc.td b/libc/spec/stdc.td
index 1720a4a3c3aaf9..b97e90d1a8ae34 100644
--- a/libc/spec/stdc.td
+++ b/libc/spec/stdc.td
@@ -781,7 +781,9 @@ def StdC : StandardSpec<"stdc"> {
         Macro<"stdc_leading_ones">,
         Macro<"stdc_trailing_zeros">,
         Macro<"stdc_trailing_ones">,
-        Macro<"stdc_first_leading_zero">
+        Macro<"stdc_first_leading_zero">,
+        Macro<"stdc_first_leading_one">,
+        Macro<"stdc_first_trailing_zero">
       ], // Macros
       [], // Types
       [], // Enumerations
@@ -810,7 +812,17 @@ def StdC : StandardSpec<"stdc"> {
           FunctionSpec<"stdc_first_leading_zero_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
           FunctionSpec<"stdc_first_leading_zero_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
           FunctionSpec<"stdc_first_leading_zero_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
-          FunctionSpec<"stdc_first_leading_zero_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>
+          FunctionSpec<"stdc_first_leading_zero_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>,
+          FunctionSpec<"stdc_first_leading_one_uc", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedCharType>]>,
+          FunctionSpec<"stdc_first_leading_one_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
+          FunctionSpec<"stdc_first_leading_one_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
+          FunctionSpec<"stdc_first_leading_one_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
+          FunctionSpec<"stdc_first_leading_one_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>,
+          FunctionSpec<"stdc_first_trailing_zero_uc", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedCharType>]>,
+          FunctionSpec<"stdc_first_trailing_zero_us", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedShortType>]>,
+          FunctionSpec<"stdc_first_trailing_zero_ui", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedIntType>]>,
+          FunctionSpec<"stdc_first_trailing_zero_ul", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongType>]>,
+          FunctionSpec<"stdc_first_trailing_zero_ull", RetValSpec<UnsignedIntType>, [ArgSpec<UnsignedLongLongType>]>,
       ] // Functions
   >;
 
diff --git a/libc/src/__support/CPP/bit.h b/libc/src/__support/CPP/bit.h
index 392fbe248138ae..596b1fb530bf93 100644
--- a/libc/src/__support/CPP/bit.h
+++ b/libc/src/__support/CPP/bit.h
@@ -268,6 +268,65 @@ SPECIALIZE_FLZ(first_leading_zero, unsigned long long, __builtin_clzll)
 
 #undef SPECIALIZE_FLZ
 
+#define SPECIALIZE_FLO(NAME, TYPE, BUILTIN)                                    \
+  template <> [[nodiscard]] LIBC_INLINE constexpr int NAME<TYPE>(TYPE value) { \
+    static_assert(cpp::is_unsigned_v<TYPE>);                                   \
+    return value == static_cast<TYPE>(0)                                       \
+               ? 0                                                             \
+               : BUILTIN(static_cast<TYPE>(value)) + 1;                        \
+  }
+
+template <typename T, typename = cpp::enable_if_t<cpp::is_unsigned_v<T>>>
+[[nodiscard]] LIBC_INLINE constexpr int first_leading_one(T value) {
+  return value == static_cast<T>(0) ? 0
+                                    : countl_zero<T>(static_cast<T>(value)) + 1;
+}
+
+#if LIBC_HAS_BUILTIN(__builtin_clzs)
+SPECIALIZE_FLO(first_leading_one, unsigned short, __builtin_clzs)
+#endif
+#if LIBC_HAS_BUILTIN(__builtin_clz)
+SPECIALIZE_FLO(first_leading_one, unsigned int, __builtin_clz)
+#endif
+#if LIBC_HAS_BUILTIN(__builtin_clzl)
+SPECIALIZE_FLO(first_leading_one, unsigned long, __builtin_clzl)
+#endif
+#if LIBC_HAS_BUILTIN(__builtin_clzll)
+SPECIALIZE_FLO(first_leading_one, unsigned long long, __builtin_clzll)
+#endif
+
+#undef SPECIALIZE_FLO
+
+#define SPECIALIZE_FTZ(NAME, TYPE, BUILTIN)                                    \
+  template <> [[nodiscard]] LIBC_INLINE constexpr int NAME<TYPE>(TYPE value) { \
+    static_assert(cpp::is_unsigned_v<TYPE>);                                   \
+    return value == cpp::numeric_limits<TYPE>::max()                                       \
+               ? 0                                                             \
+               : BUILTIN(static_cast<TYPE>(~value)) + 1;                        \
+  }
+
+template <typename T, typename = cpp::enable_if_t<cpp::is_unsigned_v<T>>>
+[[nodiscard]] LIBC_INLINE constexpr int first_trailing_zero(T value) {
+  return value == cpp::numeric_limits<T>::max()
+             ? 0
+             : countr_zero(static_cast<T>(~value)) + 1;
+}
+
+#if LIBC_HAS_BUILTIN(__builtin_clzs)
+SPECIALIZE_FTZ(first_trailing_zero, unsigned short, __builtin_ctzs)
+#endif
+#if LIBC_HAS_BUILTIN(__builtin_clz)
+SPECIALIZE_FTZ(first_trailing_zero, unsigned int, __builtin_ctz)
+#endif
+#if LIBC_HAS_BUILTIN(__builtin_clzl)
+SPECIALIZE_FTZ(first_trailing_zero, unsigned long, __builtin_ctzl)
+#endif
+#if LIBC_HAS_BUILTIN(__builtin_clzll)
+SPECIALIZE_FTZ(first_trailing_zero, unsigned long long, __builtin_ctzll)
+#endif
+
+#undef SPECIALIZE_FTZ
+
 } // namespace LIBC_NAMESPACE::cpp
 
 #endif // LLVM_LIBC_SRC___SUPPORT_CPP_BIT_H
diff --git a/libc/src/stdbit/CMakeLists.txt b/libc/src/stdbit/CMakeLists.txt
index 65d5f344307475..fa68d4a90dbb7e 100644
--- a/libc/src/stdbit/CMakeLists.txt
+++ b/libc/src/stdbit/CMakeLists.txt
@@ -4,6 +4,8 @@ set(prefixes
   trailing_zeros
   trailing_ones
   first_leading_zero
+  first_leading_one
+  first_trailing_zero
 )
 set(suffixes c s i l ll)
 foreach(prefix IN LISTS prefixes)
diff --git a/libc/src/stdbit/stdc_first_leading_one_uc.cpp b/libc/src/stdbit/stdc_first_leading_one_uc.cpp
new file mode 100644
index 00000000000000..02871595fdb6b8
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_uc.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_first_leading_one_uc -----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdbit/stdc_first_leading_one_uc.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_leading_one_uc, (unsigned char value)) {
+  return static_cast<unsigned>(cpp::first_leading_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_leading_one_uc.h b/libc/src/stdbit/stdc_first_leading_one_uc.h
new file mode 100644
index 00000000000000..58892c3f0ff298
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_uc.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_leading_one_uc -----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UC_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UC_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_leading_one_uc(unsigned char value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UC_H
diff --git a/libc/src/stdbit/stdc_first_leading_one_ui.cpp b/libc/src/stdbit/stdc_first_leading_one_ui.cpp
new file mode 100644
index 00000000000000..a6c7ef5a833914
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_ui.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_first_leading_one_ui -----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdbit/stdc_first_leading_one_ui.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_leading_one_ui, (unsigned value)) {
+  return static_cast<unsigned>(cpp::first_leading_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_leading_one_ui.h b/libc/src/stdbit/stdc_first_leading_one_ui.h
new file mode 100644
index 00000000000000..613adf4e1ff762
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_ui.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_leading_one_ui -----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UI_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UI_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_leading_one_ui(unsigned value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UI_H
diff --git a/libc/src/stdbit/stdc_first_leading_one_ul.cpp b/libc/src/stdbit/stdc_first_leading_one_ul.cpp
new file mode 100644
index 00000000000000..d1bcab5dda02a9
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_ul.cpp
@@ -0,0 +1,20 @@
+//===-- Implementation of stdc_first_leading_one_ul -----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdbit/stdc_first_leading_one_ul.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_leading_one_ul, (unsigned long value)) {
+  return static_cast<unsigned>(cpp::first_leading_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_leading_one_ul.h b/libc/src/stdbit/stdc_first_leading_one_ul.h
new file mode 100644
index 00000000000000..47c179f3fbacd1
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_ul.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_leading_one_ul -----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_leading_one_ul(unsigned long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_UL_H
diff --git a/libc/src/stdbit/stdc_first_leading_one_ull.cpp b/libc/src/stdbit/stdc_first_leading_one_ull.cpp
new file mode 100644
index 00000000000000..7be8f1051ec231
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_ull.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of stdc_first_leading_one_ull ----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/stdbit/stdc_first_leading_one_ull.h"
+
+#include "src/__support/CPP/bit.h"
+#include "src/__support/common.h"
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(unsigned, stdc_first_leading_one_ull,
+                   (unsigned long long value)) {
+  return static_cast<unsigned>(cpp::first_leading_one(value));
+}
+
+} // namespace LIBC_NAMESPACE
diff --git a/libc/src/stdbit/stdc_first_leading_one_ull.h b/libc/src/stdbit/stdc_first_leading_one_ull.h
new file mode 100644
index 00000000000000..344d03f7100f47
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_ull.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for stdc_first_leading_one_ull ----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_ULL_H
+#define LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_ULL_H
+
+namespace LIBC_NAMESPACE {
+
+unsigned stdc_first_leading_one_ull(unsigned long long value);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_STDBIT_STDC_FIRST_LEADING_ONE_ULL_H
diff --git a/libc/src/stdbit/stdc_first_leading_one_us.cpp b/libc/src/stdbit/stdc_first_leading_one_us.cpp
new file mode 100644
index 00000000000000..7a4c7e673f367f
--- /dev/null
+++ b/libc/src/stdbit/stdc_first_leading_one_us.cpp
@@ -0,0 +1,21 @@
+//===-- Implementation of stdc_first_leading_one_us -----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#in...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/81526


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